1. Field of the Invention
The present invention relates to an automatic sample injecting device (automatic sampler) for use to introduce a sample into a liquid chromatography, and a method for rinsing a needle of an automatic sampler.
2. Description of the Related Art
In the liquid chromatography (LC), the automatic sampler is used to introduce a predetermined amount of sample into a column. A sample injecting operation using the automatic sampler involves, first of all, inserting a needle into a vessel in which the sample is placed, and sucking and holding the predetermined amount of sample via the needle into a sample loop or the like. Then, the needle is moved to an injection port communicating to the column of the LC, and the held sample is injected into the injection port.
In performing an injecting operation of certain sample, if a residue of the sample used at the previous measurement adheres to the needle, a measurement error is caused by cross contamination. Therefore, the needle is rinsed before performing the injecting operation of sample. This rinsing operation is usually made by reserving a rinsing liquid in a rinsing bath and soaking the needle in the rinsing liquid as described as the related art in JP-A-9-127078 ([0004] and [0005], FIG. 2).
With this method, there is an advantage that the rinsing operation is finished in a short time, because it is only necessary that the needle is soaked in the rinsing liquid. On the contrary, there is the possibility that a sample liquid diluted by the rinsing liquid may adhere to the needle and be left on the needle, resulting in a risk that this residue may cause an error at the next measurement.
In this automatic sampler, there are various uses for the purpose of measurement where the throughput is emphasized or the measurement at high precision is desired by enhancing the rinsing performance at the expense of the throughput to some extent. In the related-art devices, such requirements were not satisfied.